The present invention relates to hydraulic valve lifters for use with internal combustion engines, and, more particularly, to a lifter-based device which accomplishes cylinder deactivation in push-rod engines.
Automobile emissions include hydrocarbons, nitrogen oxides (NOx), carbon monoxide (CO) and carbon dioxide (CO2) as a result of the combustion process. The Clean Air Act of 1970 and the 1990 Clean Air Act set goals for industry to reduce emissions from vehicles and other pollution sources. Standards set by the 1990 Clean Air Act limit automobile emissions to 0.25 grams per mile (gpm) of non-methane hydrocarbons and 0.4 gpm of nitrogen oxides. It is predicted that these standards will be reduced to one-half these levels by the year 2004. It is expected that automobiles will continue to be powered by internal combustion engines for decades to come. As the population increases, and standards of living rise, so will the demand for automobiles. This demand is predicted to be especially great in developing countries. An increasing number of automobiles will cause a proportionate increase in pollution if everything else remains constant. There is a major challenge facing automobile manufacturers to reduce undesirable emissions of hyrdrocarbons, NOx, CO and CO2 while improving fuel economy, thereby assuring the increased number of automobiles has a lessened impact on the environment. One method by which automobile manufacturers have attempted to improve fuel economy and reduce undesirable emissions is cylinder deactivation.
Cylinder deactivation is the deactivation of the intake and/or exhaust valves of a cylinder or cylinders during at least a portion of the combustion process, and is a proven method by which fuel economy can be improved. In effect, cylinder deactivation reduces the number of engine cylinders within which the combustion process is taking place. With fewer cylinders performing combustion, fuel efficiency is increased and the amount of pollutants emitted from the engine will be reduced. For example, in an eight-cylinder engine under certain operating conditions, four of the eight cylinders can be deactivated. Thus, combustion would be taking place in only four, rather than in all eight, cylinders. Cylinder deactivation is effective, for example, during part-load conditions when full engine power is not required for smooth and efficient engine operation. In vehicles having large displacement push rod engines, studies have shown that cylinder deactivation can improve fuel economy by as much as fifteen percent.
The reliability and performance of the large displacement push rod engines was proven early in the history of the automobile. The basic designs of the large displacement push rod engines in use today have remained virtually unchanged for approximately thirty years, due, in part, to the popularity of such engines; the reluctance of the consumer to accept changes in engines; and the tremendous cost in designing, tooling, and testing such engines. Conventional methods of achieving cylinder deactivation, however, are not particularly suited to large displacement push rod engines. These conventional methods typically require the addition of components which do not fit within the space occupied by existing valve train components. Thus, the application of conventional methods of achieving cylinder deactivation have necessitated major design changes in such engines.
Therefore, what is needed in the art is a device which enables cylinder deactivation in large displacement push rod engines where the device is designed to fit within the existing space occupied by conventional drive train components, thereby avoiding the need to redesign such engines.
The present invention provides a deactivation hydraulic valve lifter for use in a push rod internal combustion engine. The valve lifter can be selectively deactivated such that a valve associated with the valve lifter is not operated, thereby selectively deactivating the engine cylinder.
The invention includes, in one form thereof, a deactivation hydraulic valve lifter including an elongate lifter body having a substantially cylindrical inner wall. The inner wall defines at least one annular pin chamber therein. The lifter body has a lower end configured for engaging a surface of a cam. An elongate pin housing includes a substantially cylindrical pin housing wall and pin housing bottom. The pin housing wall includes an inner surface and an outer surface. A radially directed pin bore extends through the pin housing bottom. The pin housing is concentrically disposed within the inner wall of the lifter body such that the outer surface of the pin housing wall is adjacent to at least a portion of the inner wall of the lifter body. A plunger having a substantially cylindrical plunger wall with an outer surface is concentrically disposed within the pin housing such that the outer surface of the plunger wall is adjacent to at least a portion of the inner surface of the pin housing wall. A deactivation pin assembly is disposed within the pin bore and includes two pin members. The pin members are biased radially outward relative to each other. A portion of each pin member is disposed within the annular pin chamber to thereby couple the lifter body to the pin housing. The pin members are configured for moving toward each other when the pin chamber is pressurized, thereby retracting the pin members from within the annular pin chamber and decoupling the lifter body from the pin housing.
An advantage of the present invention is that it is received within standard-sized engine bores which accommodate conventional hydraulic valve lifters.
Another advantage of the present invention is that the deactivation pin assembly includes two pin members, thereby increasing the rigidity, strength, and operating range of the deactivation hydraulic valve lifter.
Yet another advantage of the present invention is that no orientation of the pin housing relative to the lifter body is required.
A still further advantage of the present invention is that the pin housing is free to rotate relative to the lifter body, thereby evenly distributing wear on the annular pin chamber.
An even further advantage of the present invention is that an external lost motion spring permits the use of a larger sized hydraulic element and operation under higher engine oil pressure.
Lastly, an advantage of the present invention is that lash can be robustly and accurately set to compensate for manufacturing tolerances.